gail, is the exposure compensation work in manual mode? If it works why not use shutter speed, aperture and iso to adjust? How can the exposure compensation affect the exposure?
When using manual mode, you change the shutter speed and aperture independently to change exposure. There is an indicator with a scale that changes, which looks very similar to the exposure compensation scale. It changes up and down as you change the aperture and/or shutter speed.
Here is some information on Exposure Compensation and Exposure Values:
http://www.digicamhelp.com/camera-features/advanced-settings/ec/http://www.digicamhelp.com/taking-photos/advanced-techniques/ev/In my opinion, Exposure Value and Exposure Compensation are two very important settings to understand and use in photography.
Check your camera manual for specifics.